Cold Start Noise

Have a brand new '04 325cic ( 1200 miles ) and it just recently starting making a noise during a cold start - car has sat overnight. The noise is like a bump and the engine runs rough for a few seconds. If you stop and restart the noise will not occur again and will not do so at all during the rest of the day. I am going to take it to the dealer but know it is going to be difficult to find and was wondering if anyone has had this problem before so I will be somewhat educated when I take it in.